Image forming optical system and image pickup apparatus using the same

Abstract

An image forming optical system includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a rear-side lens unit which is disposed nearest to an image. The rear-side lens unit includes a positive lens and a negative lens. The first lens unit and the third lens unit do not move in an optical axis direction. At a time of focusing, the fourth lens unit moves toward the image side. The third lens unit includes a positive lens and a negative lens. A motion blur correction lens unit is disposed in the third lens unit, and the following conditional expressions (1) and (2) are satisfied: 0.59≤| fMF/fMB |≤3.0  (1) 70.0≤ν dFFp   (2).

1 . An image forming optical system comprising, in order from an object side:
 a first lens unit having a positive refractive power;   a second lens unit having a negative refractive power;   a third lens unit having a positive refractive power;   a fourth lens unit having a negative refractive power; and   a rear-side lens unit which is disposed nearest to an image,   wherein:   at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,   the rear-side lens unit includes a positive lens and a negative lens,   the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,   at a time of focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,   the third lens unit includes a positive lens and a negative lens,   a motion blur correction lens unit is disposed in the third lens unit,   a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis, and   the following conditional expressions (1) and (2) are satisfied:
   0.59≤| fMF/fMB|≤ 3.0  (1),
 
   70.0 ≤vdFFp   (2),
 
 where, 
 fMF denotes a focal length of the third lens unit, 
 fMB denotes a focal length of the fourth lens unit, and 
 vdFFp denotes Abbe's number which is the maximum among Abbe's numbers for positive lenses in the first lens unit. 
   
     
     
         2 . An image forming optical system comprising, in order from an object side:
 a first lens unit having a positive refractive power;   a second lens unit having a negative refractive power;   a third lens unit having a positive refractive power;   a fourth lens unit having a negative refractive power; and   a rear-side lens unit which is disposed nearest to an image,   wherein:   at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,   the rear-side lens unit includes a positive lens and a negative lens,   the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,   at a time of focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,   the third lens unit includes a positive lens and a negative lens,   a motion blur correction lens unit is disposed in the third lens unit,   a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis, and   the following conditional expressions (2) and (3) are satisfied:
   70.0 ≤vdFFp   (2),
 
   3.7≤ LTL/fMF≤ 8.5  (3),
 
 where, 
 fMF denotes a focal length of the third lens unit, 
 LTL denotes a distance from a lens surface nearest to object up to an image plane, and 
 vdFFp denotes Abbe's number which is the maximum among Abbe's numbers for positive lenses in the first lens unit. 
   
     
     
         3 . An image forming optical system comprising, in order from an object side:
 a first lens unit having a positive refractive power;   a second lens unit having a negative refractive power;   a third lens unit having a positive refractive power;   a fourth lens unit having a negative refractive power; and   a rear-side lens unit which is disposed nearest to an image,   wherein:   at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,   the rear-side lens unit includes a positive lens and a negative lens,   the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,   at a time of focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,   the third lens unit includes a positive lens and a negative lens,   a motion blur correction lens unit is disposed in the third lens unit,   a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis,   the motion blur correction lens unit includes a positive lens and a negative lens, and   the following conditional expressions (4) and (5) are satisfied:
   1.5≤| LTL/fFB|≤ 9.5  (4),
 
   −2.5≤ fMB/fR≤− 0.15  (5),
 
 where, 
 fFB denotes a focal length of the second lens unit, 
 LTL denotes a distance from a lens surface nearest to object up to an image plane, 
 fMB denotes a focal length of the fourth lens unit, and 
 fR denotes a focal length of the rear-side lens unit. 
   
     
     
         4 . An image forming optical system comprising, in order from an object side:
 a first lens unit having a positive refractive power;   a second lens unit having a negative refractive power;   a third lens unit having a positive refractive power;   a fourth lens unit having a negative refractive power; and   a rear-side lens unit which is disposed nearest to an image,   wherein:   at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,   the rear-side lens unit includes a positive lens and a negative lens,   the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,   at the time focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,   the third lens unit includes a positive lens and a negative lens,   a motion blur correction lens unit is disposed in the third lens unit,   a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis,   the third lens unit includes in order from the object side, an object-side sub unit and an image-side sub unit,   the object-side sub unit includes a positive lens and a negative lens,   the image-side sub unit includes the motion blur correction lens unit, and   the motion blur correction lens unit includes a positive lens and a negative lens.   
     
     
         5 . The image forming optical system according to  claim 1 , wherein the first lens unit, the third lens unit, and the rear-side lens unit, at all times, do not move in the optical axis direction. 
     
     
         6 . The image forming optical system according to  claim 1 , wherein the motion blur correction lens unit includes a positive lens and a negative lens. 
     
     
         7 . The image forming optical system according to  claim 2 , wherein the following conditional expression (1) is satisfied:
   0.59≤| fMF/fMB|≤ 3.0  (1),
   where,   fMF denotes a focal length of the third lens unit, and   fMB denotes a focal length of the fourth lens unit.   
     
     
         8 . The image forming optical system according to  claim 1 , wherein the following conditional expression (3) is satisfied:
   3.7≤ LTL/fMF≤ 8.5  (3),
   where,   fMF denotes a focal length of the third lens unit, and   LTL denotes a distance from a lens surface nearest to object up to an image plane.   
     
     
         9 . The image forming optical system according to  claim 1 , wherein the following conditional expression (6) is satisfied:
   0.8≤| fFF/fFB|≤ 5.0  (6),
   where,   fFF denotes a focal length of the first lens unit, and   fFB denotes a focal length of the second lens unit.   
     
     
         10 . The image forming optical system according to  claim 1 , wherein the following conditional expression (7) is satisfied:
   0.45≤ fFB/fMB≤ 3.0  (7),
   where,   fFB denotes the focal length of the second lens unit, and   fMB denotes the focal length of the fourth lens unit.   
     
     
         11 . The image forming optical system according to  claim 1 , wherein the following conditional expression (8) is satisfied:
   0.8≤ fFF/fMF≤ 5.0  (8),
   where,   fFF denotes the focal length of the first lens unit, and   fMF denotes the focal length of the third lens unit.   
     
     
         12 . The image forming optical system according to  claim 1 , wherein the following conditional expression (9) is satisfied:
   0.7≤ KISA≤ 3.5  (9),
   where,   KISA=|MGISAback×(MGISA−1)|, and here   MGISAback denotes a lateral magnification of a first predetermined optical system at the time of focusing to an object at infinity, and   MGISA denotes a lateral magnification of the motion blur correction lens unit at the time of focusing to an object at infinity, and here   the first predetermined optical system is an optical system which includes all lenses positioned on an image side of the motion blur correction lens unit, and   the lateral magnification is a lateral magnification at a telephoto end in a case in which the image forming optical system is a zoom optical system.   
     
     
         13 . The image forming optical system according to  claim 1 , wherein the following conditional expression (10) is satisfied:
   2.5≤ KMBA≤ 15  (10),
   where,   KMBA=|MGMBAback 2 ×(MGMBA 2 −1)|, and here   MGMBAback denotes a lateral magnification of a second predetermined optical system at the time of focusing to an object at infinity, and   MGMBA denotes a lateral magnification of the fourth lens unit at the time of focusing to an object at infinity, and here   the second predetermined optical system is an optical system which includes all lenses positioned on the image side of the fourth lens unit, and   the lateral magnification is a lateral magnification at a telephoto end in a case in which the image forming optical system is a zoom optical system.   
     
     
         14 . The image forming optical system according to  claim 1 , wherein the following conditional expression (4) is satisfied:
   1.5≤| LTL/fFB|≤ 9.5  (4),
   where,   fFB denotes a focal length of the second lens unit, and   LTL denotes a distance from a lens surface nearest to object up to an image plane.   
     
     
         15 . The image forming optical system according to  claim 1 , wherein the following conditional expression (5) is satisfied:
   −2.5≤ fMB/fR≤− 0.15  (5),
   where,   fMB denotes a focal length of the fourth lens unit, and   fR denotes a focal length of the rear-side lens unit.   
     
     
         16 . The image forming optical system according to  claim 1 , wherein:
 the first lens unit includes in order from the object side, a first sub unit having a positive refractive power and a second sub unit, and   the second sub unit includes two lenses for which signs of refractive power are different.   
     
     
         17 . The image forming optical system according to  claim 1 , wherein:
 the first lens unit includes in order from the object side, a first sub unit having a positive refractive power, a second sub unit, and a third sub unit having a positive refractive power, and   the second sub unit includes two lenses for which signs of refractive power are different.   
     
     
         18 . The image forming optical system according to  claim 1 , wherein:
 the third lens unit includes in order from an object side, an object-side sub unit and an image-side sub unit,   the object-side sub unit includes the positive lens and the negative lens, and   the image-side lens unit includes the motion blur correction lens unit.   
     
     
         19 . (canceled) 
     
     
         20 . The image forming optical system according to  claim 4 , wherein the motion blur correction lens unit has a positive refractive power. 
     
     
         21 . The image forming optical system according to  claim 1 , wherein:
 the motion blur correction lens unit has a positive refractive power, and   the entire third lens unit is the motion blur correction lens unit.   
     
     
         22 . The image forming optical system according to  claim 4 , wherein:
 the motion blur correction lens unit has a negative refractive power, and   the image-side sub unit includes the motion blur correction lens unit and a predetermined sub unit having a positive refractive power.   
     
     
         23 . The image forming optical system according to  claim 1 , wherein:
 the motion blur correction lens unit includes not less than two lenses, and   a positive lens and the negative lens are included in the lenses not less than two lenses.   
     
     
         24 . The image forming optical system according to  claim 1 , wherein the motion blur correction lens unit includes at least two positive lenses and one negative lens. 
     
     
         25 . The image forming optical system according to  claim 1 , wherein:
 the fourth lens unit includes not less than two lenses, and   a positive lens and a negative lens are included in the lenses not less than two lenses.   
     
     
         26 . The image forming optical system according to  claim 1 , wherein an aperture stop is disposed from the image side of the second lens unit up to the object side of the fourth lens unit. 
     
     
         27 . (canceled) 
     
     
         28 . The image forming optical system according to  claim 1 , wherein:
 the rear-side lens unit includes one positive lens and one negative lens, and   one of the positive lens and the negative lens is positioned nearest to the image, and the other lens is disposed to be adjacent to the one of the positive lens and the negative lens.   
     
     
         29 . (canceled) 
     
     
         30 . The image forming optical system according to  claim 1 , wherein the following conditional expression (12) is satisfied:
   0.015≤ LIS/LTL≤ 0.2  (12),
   where,   LIS denotes a total thickness on an optical axis of the motion blur correction lens unit, and   LTL denotes a distance from the lens surface nearest to object up to the image plane.   
     
     
         31 . (canceled) 
     
     
         32 . The image forming optical system according to  claim 1 , wherein:
 the image forming optical system is a macro lens, and   the focusing is carried out by moving the second lens unit and the fourth lens unit toward the image side.   
     
     
         33 . The image forming optical system according to  claim 1 , wherein:
 the image forming optical system is a macro lens,   the macro lens includes in order from the object side, the first lens unit, the second lens unit, the third lens unit, the fourth lens unit, and the rear-side lens, and   the macro lens is a five-unit type optical system which includes no other lens unit and in which distances between lens units vary.   
     
     
         34 . The image forming optical system according to  claim 1 , wherein:
 the image forming optical system is a zoom lens of which an angle of view varies,   zooming toward a telephoto side is carried out at least by moving the second lens unit toward the image side and by moving the fourth lens unit, and   focusing to an object at a close distance is carried out by moving the fourth lens unit toward the image side.   
     
     
         35 . (canceled) 
     
     
         36 . (canceled) 
     
     
         37 . An image pickup apparatus comprising:
 an optical system; and   an image pickup element which has an image pickup surface, and which converts an image formed on the image pickup surface by the optical system to an electric signal, wherein the optical system is the image forming optical system according to  claim 1 .